Overview

Project Highlights:

  • To study the pathways of micro- and nanoplastics in aquatic life using zebrafish as a model system;
  • To investigate how the plastic particles taken in by zebrafish impact on foraging, social and reproductive behaviour;
  • To learn how these particles alter the chemical environment and gene expressions of the containing organisms and thus prospect how micro- and nanoplastics may have an effect on human health

 

Overview

By 2015, humans had generated 8.3 billion metric tons of plastics, 6.3 billion tons of which had already become waste. Of that waste total, only 9 percent was recycled, 12 percent was incinerated and 79 percent accumulated in landfills or the natural environment. The quantity of plastics on our planet will continue to grow, reaching 40 billion tons by 2050. Plastics is now a major feature of the changed, anthropocene, state of our planet.

While attention has now been drawn to macro-plastic debris accumulating in oceanic gyres and on coasts, or causing damage to wildlife, the insidious effects of plastics at a much smaller scale, the micro- and nanoplastics, go relatively unnoticed. These particles come from a variety of sources, including from larger plastic debris that degrades into smaller and smaller pieces. Although they are largely unseen, small particles (<1 mm) have become ubiquitous in the marine environment over several decades. They can have negative consequences for marine ecosystems and humans through physical damage to organisms that ingest them and chemical transfer of toxicants. Recent studies have also shown that micro-and nanoplastics can interact directly with biological systems, e.g., with proteins that are important for fat metabolism, immune defense and blood coagulation, and may alter the behaviour, physiology and metabolism. Plastic particles have been found in a third of UK-caught fish such as cod, haddock, mackerel and shellfish, and people who eat seafood ingest up to 11,000 tiny pieces of plastic every year, and have been recently identified in human stools.

Plastic pollution has emerged as a real threat to Earth’s ecosystems, especially in the ocean. However, little is known so far about micro- and nanoplastics once they enter biological systems. It has been hypothesized that ingestion of microplastic increases exposure of aquatic organisms to hydrophobic contaminants but how these particles transport, accumulate and interact with organisms, and how these impact on the chemical environment with consequent changes to growth, behaviour, reproduction, and physiology, remain unclear. 

Figure 1: Pinpointing plastic’s path to the deep sea – a giant larvacean that has comsumed microplastic beads.

Methodology

This is multidisciplinary research involving chemistry, nanoscience and biology, which will be carried out through collaborations between the teams in Chemistry and NPB at UoL. The project will use zebrafish as a model system, and will focus on particles of commonly used plastics such as polyethylene terephthalate (PET), polyethylene (PE) and polystyrene (PS). Particles ranging from 50 nm – 1 mm will be prepared by a dissolution and reprecipitation procedure. To enhance the visibility and ease the detection of particles in fish, highly fluorescent nanoparticles will be synthesized and will be incorporated into plastic particles.

The project will start by studying the pathways of plastic particles in zebrafish and how they accumulate by using confocal microscopy. By comparison with zebrafish in clean water, the impact on behaviours such as foraging, social and reproduction will be monitored. In addition, we will measure behaviours including aggression, anxiety, boldness, sociality and learning using protocols already established at NPB. The changes on chemicals and gene expressions of organisms that host plastic particles will also be studied, allowing the prediction of potential hazards of micro- and nanoplastics to human health.

Training and Skills

The student will receive wide-ranging training in this project, including  a one-day enterprise and entrepreneurial activity, the procedures to synthese micro- and nanoparticles and fluorescent metal-semiconductor nanomaterials, characterisation techniques, measurements of zebrafish behaviour, neurochemistry and gene expression changes, etc. The student will benefit from the extensive expertise in nanoscience at Chemistry and in behavioural neuroscience at NPB. Facilities for the work at UoL are excellent and include an extremely well-equipped open-plan laboratory at Chemistry and state-of the art aquariums and behavioural setups in available in NPB. Upon finishing the project the student will be equipped with a full set of skills in nanoscience and behavioural neuroscience.

 

Timeline

Year 1: The student will learn how to synthesise plastic particles with good control over size and shape. Meantime, she/he will be involved the preparation of fluorescent nanoparticles with a noble metal core and a semiconductor shell in order to enhance the visibility of plastic particles. The student will also be involved in trainings offered by CENTA.

Year 2:  Conducting early experiments using zebrafish as the model system to study the transport and accumulation of plastic particles. Particles with different sizes will be investigated, with focus on the dependence of transport properties on the sizes. We also intend to learn whether plastic particles can be ejected when the fishes fed with plastic particles return to fresh water. The student will also present in conferences to disseminate new results.

Year 3:  Study the impact of plastic particles on the chemical environment in the biological systems. This is also associated with measurements of the behaviour, the reproduction rates, the growth rates and gene expression changes in order to provide further insights into the chemistry and biology involving plastic particles. The student will also disseminate the research via publications and conferences, and will start to write up the thesis.

Partners and collaboration (including CASE)

We already have collaborations with several industrial partners in relevant areas such as polymer degradation (with Polymateria). A specific aim of the project is to predict how the micro- and nanoplastic particles can influence human health, which might have strong indication for the consumption of plastic-related goods such as chewing gums and toothbrushes and may have strong influence of the corresponding industry. We intend to cultivate this interest to generate commercial sponsorship and to explore converting the project to another CASE studentship.

 

Further Details

Potential applicants are welcome to discuss the project informally and obtain further information from the project supervisors:

Dr Shengfu Yang, Department of Chemistry, University of Leicester; sfy1@le.ac.uk.

Dr Will Norton, Department of Neuroscience, Psychology and Behaviour, University of Leicester; whjn1@le.ac.uk.